1. Field of the Invention
The present invention relates to a power supply technique and, more particularly, to a power supply apparatus suited to stably supply a voltage to the electrostatic chuck of a substrate holder rotatably installed in a vacuum processing chamber, and a deposition method using the power supply apparatus.
2. Description of the Related Art
In a vacuum processing apparatus such as a deposition apparatus that deposits various films and the like on a substrate, or a dry etching apparatus that etches films and the like deposited on a substrate, it is necessary to rotate a substrate and improve temperature control for controlling the temperature of the substrate at a desired temperature in order to increase the uniformity of processing on the substrate surface. The vacuum processing apparatus generally incorporates a heating device or cooling device for substrate temperature control in a substrate holder in many cases. To increase the substrate temperature control accuracy, it is important to increase the adhesion between a rotatable substrate holder and a substrate mounted on and fixed to the substrate holder, and accurately set the substrate at a desired temperature by supplying a gas between the substrate holder and substrate. Electrostatic attraction using an electrostatic chuck is effective as a means for fixing a substrate mounted on the substrate holder. However, attaching the electrostatic chuck to the substrate mounting surface of the rotating substrate holder requires a power supply mechanism capable of stably supplying electric power (a DC voltage and a bias voltage applied to a substrate in addition to the DC voltage, to be referred to as a DC voltage and the like hereinafter) for operating the electrostatic chuck.
In a vacuum processing apparatus having a substrate rotating mechanism, a rotating strut that supports a substrate holder installed in a vacuum chamber extends through the wall of the vacuum chamber, and is rotatably held such that a magnetic fluid seal secures airtightness between the rotating strut and the wall surface of the vacuum chamber. As the power supply mechanism that supplies the bias voltage to a substrate mounted on the substrate holder in the vacuum chamber, a conductive electrode member connected to the power supply is generally urged against the circumferential surface of the rotating strut by a point contact structure (e.g., Japanese Patent Laid-Open No. 2002-339064). High-frequency power supplied from the power supply is supplied in the order of the conductive electrode member having the point contact structure, the rotating strut, and the substrate holder, and finally applied to the substrate on the substrate holder.
Recently, to further improve the performance and increase the degree of integration of magnetoresistive effect elements such as a TMR (Tunneling MagnetoResistive) element and MRAM (Magnetic Random Access Memory) and other high-performance elements, demand has arisen to increase the uniformity of film quality such as the crystal grains and stress and the uniformity of film thickness, thereby further improving its characteristics. For this purpose, micropatterning processes such as deposition and dry etching performed with a substrate being rotated are essential process conditions. It is also necessary to more accurately control and supply DC voltage and the like to a substrate mounted on the rotating substrate holder.
Unfortunately, it is difficult for conventional power supply mechanisms to supply sufficiently high electric power because a point contact structure is used between the rotating strut of the substrate holder and the conductive electrode member. Also, in this structure, a carbon electrode of the conductive electrode member is brought into contact with the circumferential surface of the rotating strut in rotation. Therefore, increasing the contact area of the electrode limits the rotation of the rotating strut and makes the rotation unstable. In addition, deterioration caused by the wear heat of the carbon electrode makes power supply to a substrate and the like unstable. If power supply to a substrate becomes unstable, the bias voltage on the substrate surface becomes nonuniform, and this interferes with uniform and homogeneous deposition. This also poses the additional problems of charge-up occurring on the substrate surface which breaks element functions, and an inability to raise the etching rate.